It is well known that the control of rodents, such as gophers, mice, rabbits, and the like, is of widespread concern throughout the agricultural industry, and the commercial search for an efficient and effective rodenticide continues. See Lazar et al. (1986) U.S. Pat. No. 4,581,378. Large scale commercial agricultural ventures require in addition a high degree of cost effectiveness.
However, the general direction of the search appears to be in the area of modifying food substances, typically grain materials, so that they become toxic to rodents while at the same time remaining attractive to them. For example, see Lapham et al. (1970) U.S. Pat. No. 3,544,677 and Hagerman et al. (1981) U.S. Pat. No. 4,287,183, as well as Lazar et al. cited above. Even Lusby (1974) U.S. Pat. No. 3,816,610, suggests the use of a conventional rodent attracting food substance such as grain or dried blood in his otherwise unconventional method.
No known rodenticide makes use of rodent toxic plant materials in a distributable form as the primary ingredient of a rodenticide composition. Edmonds (1934) U.S. Pat. No. 1,952,977, discloses the rodenticidal use of an extract of the plant Red Squill. However Edmonds' disclosed method of use of the extract as a rodenticide requires that it be mixed a substantial quantity of some rodent edible food such as bread or toast. Even the extracted Red Squill plant material which is disclosed by Edmonds for possible use as a rodenticide after it is dried, apparently requires a greater than 50% by weight admixture of molasses in order to be attractive to rodents. Neither is it known to make a pelletized rodenticide exclusively, or nearly exclusively, from rodent toxic plant materials.
Accordingly it is an object of the invention to provide a distributable rodenticide in pelletized form which consists primarily or exclusively of rodent toxic plant materials with only a small percentage by weight, if any, of rodent attracting substances.
In addition to Red Squill, Euphorbia lathyrus, also known as Caper Spurge and as Nature's Farewell, has high concentrations of rodent toxic substances. It is a fairly easy to grow and inexpensively produced and harvested weed-like plant. The Euphorbia lathyrus plant is relatively prolific in diverse growing environments and, when planted as a hedge around small home gardens, has been reported to serve as an effective rodent deterrent on this limited scale. It appears to do so in this limited application because the roots spread out beneath the growing Euphorbia plants and interlock with the roots of adjacent Euphorbia plants when they are planted closely enough together (the root radius growing to some 2 feet in a mature plant). Burrowing rodents who desire to enter gardens surrounded by such Euphorbia lathyrus hedges must ordinarily burrow into and through the root fibers of the Euphorbia lathyrus plant, necessarily ingesting some of the toxic root fibers. The rodents are thereby either discouraged from further burrowing or are killed by the toxic effect of the milky white latex-like substance present in the root fibers. The same milky white toxic substance exists throughout the Euphorbia lathyrus plant including the above ground portions of the plant, such as the stems and leaves, and is particularly concentrated in the seeds. However it is not known that rodents will attempt to consume any portion of a Euphorbia lathyrus plant, except for fortuitous ingestion of root fibers which happen to be in their way as they burrow from one location to another. Therefore there has been no suggestion in the art that Euphorbia lathyrus might serve as a distributable rodenticide.
It is therefore a further object of the invention to provide a distributable rodenticide in the form of chopped and pelletized plant materials from the Euphorbia lathyrus plant.
It is another object of the invention to provide a method of preparing a pelletized rodenticide from rodent toxic plant materials, and a method of controlling rodents with the pelletized rodenticide.